The research presented in this dissertation focused on the microbial ecology of the subglacial discharge from the Taylor Glacier in the McMurdo Dry Valleys, Antarctica. The major objectives of my research were to 1) define the biogeochemistry of the subglacial outflow 2) describe the microbial diversity of the subglacial outflow and 3) examine the impact of subglacial outflow on the geochemistry and biology of the west lobe of Lake Bonney, a lake that abuts the glacier. The subglacial outflow from the Taylor Glacier is known as Blood Falls owing to a visible accumulation of iron-oxides at the point where it flows from the snout of the glacier. The subglacial reservoir is thought to originate from the Pliocene Epoch (~5 Mya) when the dry valleys were fjordlands. The episodic release of subglacial water at Blood Falls provides a sample of what is believed to be ancient seawater trapped in the upper Taylor Valley and eventually covered by the Taylor Glacier as it advanced. Biogeochemical measurements, culture-based techniques, and molecular analysis (based on 16S rDNA sequences), were used to characterize microbes and chemistry associated with the subglacial outflow.